Retractable extension for fixed ladders



July 15, 1969 J J. meems RETRACTABLE EXTENSION FOR FIXED LADDERS Filed March 20, 1968 2 Sheets-Sheet 1 NQET JOSEPH J. HIGGINS y 15, 1969 J. J. HIGGINS 3,455,414

RETRACTABLE EXTENSION FOR FIXED LADDERS Filed March 20. 1968 2 Sheets-Sheet 2 I58/ g /BO |26 INVENTOR JOSEPH J. HIGGINS moRNEY i In QWZA United States Patent 3,455,414 RETRACTABLE EXTENSION FOR FIXED LADDERS Joseph J. Higgins, 5812 Maryhurst Drive, Hyattsville, Md. 20782 Filed Mar. 20, 1968, Ser. No. 714,507 Int. Cl. E06c 7/18 U.S. Cl. 182-106 11 Claims ABSTRACT OF THE DISCLOSURE A retractable extension for fixed ladders having a guide mounted on the ladder, and an extension member slidably disposed in the guide to move between an extended and retracted position. A catch including a key on one end of one member and a slot on the other end of the other member cooperate to retain the extension member in the extended position. The slot has an arcuate cam surface disposed to laterally translate the key to a catc position when the extension member is moved from the retracted position to the extended position.

BACKGROUND OF THE INVENTION This invention relates generally to ladders and more particularly to a retractable side rail extension safety device for fixed, relatively vertical ladders.

Fixed ladders find wide utility throughout industry, generally in permanent installations wherein periodic access to a different level is required for the purposes of maintenance, operation of equipment, inspection or the like. Such fixed ladders are most often used in situations wherein sufficient lateral space is not available to enable the use of more conventional Stairways, or wherein the frequency or type of use does not economically dictate employment of more conventional stairways. Such ladders find particular applicability when mounted on the side of manholes or other vertical tunnels, to the exterior or interior of fluid containing tanks or to the exterior or interior of buildings, towers or other such structures.

In cases where such ladders are installed on the interior of a tank, building or in a manhole, it is incumbent that the upper ends of the side rails terminate at a point immediately below the higher level to which the ladder provides access, since a cover, hatch or the like must generally be installed when the ladder is not in use. In other cases, it is also often advisable to terminate the upper end of the side rails below the higher level for aesthetic purposes or to prevent interference with activities at the upper level. In any case, the prior art fixed ladders present serious safety problems in that it is difficult for personnel either ascending or descending the ladder to maintain balance when mounting or demounting the upper end of such ladders due to the normal lack of a hand hold or grip at that point.

SUMMARY OF THE INVENTION This invention provides a novel device which avoids the disadvantages of prior art fixed ladders by providing a retractable side rail extension for the upper end of the ladder.

This invention provides a novel side rail extension for fixed ladders which is inexpensively fabricated, easily installed, and simple in operation, by furnishing an extension member slidable in a side rail guide provided with a dependable and easily operated catch mechanism for maintaining the extension in its extended position during use.

The invention also provides a novel catch mechanism for the side rail extension member of a fixed ladder which is simply operated and provides reliable and safe performance by furnishing a slot member on one member which receives a key disposed on the other member and which is formed to safely and automatically earn the key li)nto a catch position on extension of the extension mem- A preferred embodiment of the invention comprises a tubular guide mounted to the side rail of the upper end of the ladder; an elongated extension member disposed in the guide and slidable between an extended and a retracted position; a catch mechanism comprising a slot in the guide having a vertical portion which terminates, at the upper end thereof, in an arcuate portion; and a key extending laterally from the lower end of the extension member receivable in the slot; the slot being formed to automatically translate the key laterally to a catch position when the extension member is moved to the extended position.

In another embodiment of the invention, biasing means are provided to normally urge the extension member toward the extended position and a second catch mechanism is provided to maintain the extension member in the retracted position against the influence of the biasing means.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings wherein like components throughout the figures thereof are indicated by like numerals and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side elevational view of a preferred form of the invention in the extended position;

FIGURE 2 is a front elevational view of the embodi ment of FIGURE 1 in the retracted position;

FIGURE 3 is an enlarged fragmentary detailed view of a portion of the embodiment of FIGURE 2;

FIGURE 4 is a transverse sectional view taken along the lines 4-4 of FIGURE 3;

FIGURE 5 is a view similar to FIGURE 3 illustrating a modified form of the invention;

FIGURE 6 is a side elevational view of FIGURE 5; and

FIGURE 7 is an enlarged sectional view taken along the lines 77 of FIGURE 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now generally to FIGURES 1 and 2 of the drawings, a ladder indicated generally at 10 and comprising side rails 12 and 14 and horizontal rungs 16, is fixed to the wall of a vertical structure 18 by means of brackets 20 in a conventional manner. As can be seen in FIGURE 1, the side rails 12 and 14 terminate just below a higher level 22 to which the ladder provides access.

The ladder 10 is provided with a tubular guide 24 mounted adjacent the upper end of the side rail 12 by means of U-bolts 26. As will be described hereinafter, the invention is applied to only one side rail of the ladder 10; however, it should be understood that a similar structure may be applied to each side rail of the ladder if so desired. The guide 24 has, provided in the lower end thereof, a slot indicated generally at 28, and slidably receives an extension member 30' therein. As is best seen in FIGURE 2, the extension member 30 is provided with an enlarged grip 32 at the upper end thereof, a laterally extending stop 34 proximate the grip, and a laterally extending key 36 proximate the lower end thereof.

Although the assembly of the aforedescribed structure is by threaded connectors, it should be understood that fabrication may be accomplished by any suitable means such, for example, as by welding, rivetting or the like. The structure may also be fabricated as an integral unit by means of casting, machining or the like if so desired.

Although the cross-sectional configuration of the extension member 30 and the guide 24 is illustrated as cylindrical, the configuration may be of any suitable configuration so long as both transitional and rotary sliding motion between the member and guide is provided.

As may be seen by reference to FIGURE 2, the key 36 is preferably of a length suitable to engage the forward edge of the side rail 12 as illustrated. The length of the extension member 30 may be as desired and is preferably of a length providing an extension above the top of the ladder suitable to furnish adequate leverage and support for a man of average height mounting the ladder.

As an example, an extension above the surface 22 of approximately 3 feet, 9 inches, has been found to be adequate. Such an extension can be provided with components of the following dimensions:

Length of guide 24 2 feet. Length of extension member 6 feet, 9 inches. Distance of key 36 from bottom of extension member 30 3 inches. Effective depth of slot 28 3 inches. Distance between upper end of guide 24 and level 22 1 foot.

Referring now more particularly to FIGURES 3 and 4 of the drawings, the slot 28 is formed with an entrance portion, indicated generally at 38, leading into an arcuate portion, generally shown at 40, which portion extends through approximately 180 to terminate in a catch portion 42. The catch portion 42 is laterally displaced from the terminus of the arcuate portion to form a transverse surface 44 at the upper edge thereof. The entrance portion 38 comprises an upwardly tapering lead-in portion 46 leading into a vertical portion 48. As can be seen by reference to the figures, the entrance portion 38 is generally aligned with the forward edge of the side rail 12 so that, as shown in phantom, the key 36 can ride on the forward edge and thus be guided into the slot.

The arcuate portion 40 is in the form of a continuous curve with an upper surface comprising an are about the center disposed on line A, while a lower surface 52 is initiated by an arc of smaller radius drawn about a center disposed on line B and terminates in a downwardly sloping surface. As can be seen from FIGURE 3, line B is laterally displaced from line A a distance 01 toward the vertical portion 48 so that, effectively, the arcuate portion 40 is increased in width from the point of intersection with the vertical portion 48. This configuration provides an operational benefit in that, as the extension member 30 is elevated toward the extended position (FIGURE 1), the key 36 enters the vertical portion 48 of the slot 38 and is then cammed laterally by the surface 50 to a point wherein the center of the key is coincident with the line A. Release of the extension member 30 at this point automatically brings the key 36 into engagement with the portion of the lower surface 52 sloping downwardly toward the catch portion 42, thereby further camming the key toward the catch portion. The aforedescribed structure thereby provides safe and reliable retention of the extension member 30 in the extended position by a simple upward movement thereof to the uppermost extremity followed by a release of the extension member to provide automatic movement of the key 36 into the catch portion. The transverse surface 44 blocks removal of the key 36 from the catch portion 42 by simple vertical movement of the extension member 30, thereby providing safe and reliable retention of the extension member in the extended position. Return of the extension member 30 to the retracted position (FIGURE 2) must be accomplished by intentional movement of the extension member 30 according to the following program:

(1) Lift extension member 30 slightly to center the key 36 in the catch portion 42;

(2) Rotate the extension member counterclockwise (as viewed looking downwardly from the top);

(3) Lift extension member until stopped;

(4) Slowly lower extension member with simultaneous rotation thereof in a clockwise direction.

Obviously other suitable configurations of the slot 28 may be provided as desired without exceeding the scope of this invention so long as the described relationship between the centerlines of the upper surface 50 and the lower surface 52 are maintained or the arcuate portion of the slot is widened through at least from the point of intersection with the vertical portion 48. It should also be obvious that, if so desired, the structure may be reversed, for example, by placing the key 36 on the guide 24 and the slot 38 in the extension member 30 without altering the operation of the invention.

With reference to the stop 34, it is seen that a depending guard 54 is provided on the other extremity thereof, extending in spaced relationship to the guide 24. Such a guard rovides benefit in that, if a users hand accidentially is on the upper edge of the guide 24 when the extension 30 is released from the extended position, the guard 54 will serve to clear the hand away from the guide prior to engagement of the stop 34 thereby precluding serious injury to the user.

By reference now to FIGURE 2, the general alignment of the slot 28 with the side rail 12, as described above, provides an additional benefit in that, with rotation of the extension member 30 to the clockwise extremity, the key 36 will ride on the forward edge of the side rail and thus be guided into the lower or lead-in portion 46 of the slot, thereby providing simplicity of operation of the dev1ce.

The extension member may be operated either from below by a person ascending the ladder or from above by a person descending the ladder, as desired.

In FIGURES 5 through 7 a variation in accordance with the invention is illustrated wherein components thereof corresponding to like components of the preceding embodiment are indicated by like numerals only of the next higher order.

The primary distinction of the embodiment of these latter figures over that of the preceding figures lies in the provision of a biasing means to normally urge the extension member in the extended position. Such means comprises, in the illustrated embodiment, a counterweight 156 suspended from a cable 158. The cable is entwined around a pulley assembly 160 and attached, at the other end thereof, to the key 136. The pulley assembly 160 is, in turn, attached proximate the upper end of the guide 124, by means of a bracket 162 mounted on, for example, the upper U-bolt 126. The Weight of the counterweight 156 is on the order of the weight of the extension member 130, and preferably slightly exceeds the weight to overcome friction loses and, if desired, to provide automatic extension of the apparatus upon release thereof. The slot 138 of the embodiment of these figures differs in configuration from the slot of the previously described figures in that the arcuate portion 140 is in the form of an S-shaped reversed curve as opposed to the continuous curve of the prior embodiment. The curve reverses itself and terminates in a catch portion 142 above the upper extremity of the vertical portion 148. The catch portion 142 is displaced from the terminus of the arcuate portion 140 so that the transverse surface 144 is provided to block simple vertical removal of the key from the catch portion 142.

As can be readily seen by FIGURE 5, upward movement of the extension member 130 introduces the key 136 through the lead-in portion 146 and vertical portion 148 around the arcuate portion 140 into the catch portion 142 With the application of a simple upward vertical force. In addition to a force to overcome the force of the weight 156, retraction of the extension member 130 requires a definite programmed movement of the extension member 130 first in a counterclockwise direction and then, with downward pressure, movement in a clockwise direction. As indicated in phantom, a knock-out section 164 may be provided in the guide 124 to make the guide adaptable to either the embodiment of FIGURES 1 through 4 or 5 through 7, thereby simplifying the logistics of supply for the device, A similar knock-out section may also be provided in the upper portion of the slot 138 so that a selection of either configuration may be made at the time of installation of the device.

In order to provide retention of the extension member 130 where desired, a second slot 166 is provided in the upper end of the guide 124 and a second key 168 extends laterally from the upper end of the extension member. As may be seen, the slot configuration is similar to the slot 38 in the aforedescribed embodiment and operates in an identical but inverted fashion to provide a releasable catch for the extension member 130. Other suitable catch means such, for example, as spring detents or the like may obviously be provided in lieu of the slot and key 166 and 168 if so desired.

It should also be noted that the arrangement of the cable 158 is such that a clockwise rotational bias is maintained on the extension member 130 since at attached end of the cable is suspended most proximate the side rail 112. The key 136 is therefore normally biased against the side rail 112 in the retracted position and against the innermost surface of the catch 142 in the extended position, thereby providing an added safety factor and greater ease of operation of the device. It should be noted that, with this arrangement and by proper design of the camming surfaces of the slot 138 and proper weight in the counterweight 156, the extension and locking of the extension member 130 in the extended position can be achieved substantially automatically simply by release of the extension member 130. T husly, by eliminating the key 168 and utilizing a hatch or cover as the sole means for retaining the extension member 130 in the retracted position, automatic extension of the device can be achieved merely by opening or removing the cover.

Obviously biasing means other than those specificially illustrated may also be supplied if found suitable. Such biasing means could take the form of springs, or hydraulic or pneumatic motors without exceeding the scope of the invention.

What has been set forth above is intended primarily as exemplary of embodiments in accordance with the invention to enable those skilled in the art in the practice thereof. It should therefore be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.

What is new and therefore desired to be protected by Letters Patent of the United States is:

1. An extension device for ladders having side rails comprising:

guide means attachable to a ladder side rail;

an elongated extension member disposed in said guide means and longitudinally slidable between a first position and a second position therein;

catch means to releasably retain said extension member in said second position including:

a key disposed on one of said members;

the other of said members having a slot formed therein,

said slot disposed to receive said key when said extension member is moved from said first position to said second position, said slot comprising an entrance portion leading into a curved portion extending through an are greater than about 90 and terminating in a catch portion, one edge of said curved portion engaging said key upon movement of said members from said first position to said second position for lateral translation thereof into said catch portion.

2. An extension device in accordance with claim 1 wherein said entrance portion includes a substantially vertical portion and wherein said catch portion comprises a notch displaced laterally with respect to said arcuate portion to form a transverse surface for blocking direct vertical displacement of said key therefrom.

3. An extension device in accordance with claim 1 wherein the width of said vertical portionis generally on the order of the diameter of said key and said entrance portion further comprises an outwardly tapering lower lead-in portion intersecting said vertical portion.

4. An extension device in accordance with claim 2 wherein the width of said arcuate portion increases from a width substantially equal to that of said vertical portion at the point of intersection therewith.

5. An extension device in accordance with claim 1 wherein said guide means comprises a tubular member disposable parallel to one of said side rails and wherein said slot is formed through a surface in said tubular member with said entrance portion intersecting the lower end thereof, said key comprising a substantially circular lug extending transversely from the lower end of said extension member.

6. An extension device in accordance with claim 5 in combination with a ladder having side rails, said tubular member disposed parallel to said side rails, the entrance portion of said slot being generally aligned with a plane extending between the centerline of said tubular member and an edge of one of said side rails.

7. An extension device in accordance with claim 1 wherein said arcuate portion is in the \form of a constant curve.

8. An extension device in accordance with claim 1 wherein said arcuate portion is generally in the form of an S-shaped curve.

9. An extension device in accordance with claim 8 wherein biasing means are provided to normally urge said extension member toward said second position.

10. An extension device in accordance with claim 9 wherein catch means are disposed between said guide means and said extension member for releasable retention thereof in said first position.

11. A retractable extension for fixed relatively vertical ladders having side rail members comprising:

an elongated extension member proximate the upper end of at least one of said side rails, said extension member being slidable between a retracted position within the limits of said side rail member and an extended position extending above the top of said side rail member;

means to bias said extension member in said extended position; and

rigid catch actuated when said extension member is moved to said extended position means to releasably retain said extension member in said extended position.

References Cited UNITED STATES PATENTS 421,914 2/1890 Dormitzer 182-106 2,640,641 6/ 1953 Tepper 182-106 3,288,247 11/1966 Barness 182106 3,305,045 2/ 1967 Schlecht 182-106 FOREIGN PATENTS 205,412 10/1923 Great Britain.

REINALDO P. MACHADO, Primary Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,455,414 July 15, 1969 Joseph J. Higgins It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

--. Column 6,

"at" should read the after Column 5, line 21,

insert means line 54,

line 53, after "catch" "position" cancel "means".

Signed and sealed this 21st day of April 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR. 

